Got the same problem.
Mint Linux here with the Mozilla 11.0
Some time ago I refreshed main page and it told me that there is maintenance going on.
Now when I go to www.mobileread.com I am still redirected to http://www.mobileread.com/upgrade.html , except that the page doesn't exist anymore.

Opera and Chrome do not have a problem, but I didn't use those to visit main page during shutdown.

Happened to me as well using Dolphin HD on an Android tablet. But only once, closing that tab and reopening it made it OK.